In recent years, product development and mass production facilities development have been actively pursued with regard to a GMR film which is considered very valuable for use in a conventional high precision magnetic sensor and a reading magnetic head of HDD since the GMR film has the magnetoresistive ratio of more than four times and the sensitivity of more than five times when compared with a conventional ferromagnetic magnetoresistive effect film (referred to as "MR film" hereafter).
An artificial latticed multi-layer film deposited with GMR films has a plurality of magnetic metal films and a plurality of non-magnetic metal films formed into a multi-layer structure. More specifically, a magnetic metal layer formed of a metal alloy layer of one kind to three kinds selected from the group of ferromagnetic metal materials of Ni, Fe and Co and a non-magnetic metal layer formed of one selected from the group of Cu, Ag, Au, Ru, Cr, Pt and the like are alternately laminated one over the other with each layer thickness measuring 5 .ANG. to 50 .ANG., which is less than the mean free path of electron, so as to have each respective magnetic metal layer provided with an antiparallel electron spin by having respective magnetic metal layers coupled antimagneticly via the non-magnetic metal layers and to have the electron spin changed in direction according to the external magnetic field, thereby bringing about a big differential in the mean free path of conduction electron with a resulting realization of the GMR.
Next, a description is given to an artificial latticed multi-layer film having the GMR with reference to drawings.
FIG. 6 is a cross-sectional view of an artificial latticed multi-layer film having the GMR Reference numeral 1 is a substrate formed of high resistance Si, glass and the like. Reference numeral 2 is a underlying metal layer of Cr, W and the like formed on the upper surface of the substrate 1 by film deposition. Reference numerals 3 and 4 are a magnetic metal layer and a non-magnetic metal layer, respectively. These layers 3 and 4 have been formed by alternately laminating respective magnetic metal films and non-magnetic metal films one over the other by film deposition according to a sputtering method up to around 15 layers of the films, respectively, with the lowest layer of the films disposed on the upper surface of the underlying metal layer 2. Reference numeral 5 is a protective film disposed on the upper surface of the non-magnetic metal layer 4 situated on the upper most surface of the magnetic metal layers 3 and non-magnetic metal layers 4 alternately laminated on the substrate 1. At this time, each respective layer of the magnetic metal layer 3 and non-magnetic metal layer 4 deposited by sputtering is allowed to present the configurations of a uniformly and smoothly formed film when compared with the layer deposited according to a method of vacuum thermal deposition employing electron beam heating or resistance heating because the kinetic energy for bombarding the material molecules onto the substrate is large. Controlling of the film thickness is easy and consistent reproducibility is possible and, therefore, the foregoing processing method is considered most appropriate in forming an artificial latticed multi-layer film having a multi-layered artificial lattice structure. Accordingly, the multi-layered films deposition by sputtering is considered one of the most promising candidate methods for the future mass production of artificial latticed multi-layer films.
Next, relative to the artificial latticed multi-layer film structured as above, a description is made on an artificial latticed multi-layer film deposition apparatus for disposing a magnetic metal layer and a non-magnetic metal layer, which form an essential part of the artificial latticed multi-layer film, by film deposition with reference to drawings.
As the prior art artificial latticed multi-layer film deposition apparatus, such an apparatus as disclosed in Japanese Patent Application Unexamined Publication No. H07-57933 is known.
FIG. 7 is a schematic sketch to show the structure of a prior art artificial latticed multi-layer film deposition apparatus.
In FIG. 7, reference numeral 11 is a vacuum container. Reference numerals 12 and 13 are a Cu target and a Co target disposed on the bottom surface inside of the vacuum container 11, respectively. Reference numeral 14 is a shutter disposed by opposing to the Cu target 12 formed of a non-magnetic metallic material and the Co target 13 formed of a magnetic metallic material. Reference numeral 15 is a turntable operated by making rotatable, with one end thereof held by the upper side of the vacuum container 11 and the other end provided with a substrate holder 16 that holds a substrate (not shown in the drawing) by snapping in, thereby allowing the substrate to pass the upper surfaces of the Cu target 12 and Co target 13 alternately.
Relative to the artificial latticed multi-layer film structured as above, a description is made below on how the film deposition is performed.
First, Ar gas is introduced into the vacuum container 11 with the gas pressure maintained at about 0.5 Pa after the background vacuum of the vacuum container 11 has been adjusted to 1.3.times.10.sup.-4.about.9.times.10.sup.-4 Pa.
Then, the Cu target 12 formed of a non-magnetic metallic material and the Co target 13 formed of a magnetic metallic material are made to discharge at the same time, a substrate is snapped in the substrate holder 16 and the turntable 15 is rotated so that the substrate passes the upper surfaces of the Cu target and Co target alternately, thereby depositing magnetic metal layers and non-magnetic metal layers alternately for lamination.
However, with the above prior art artificial latticed multi-layer film deposition apparatus, the film deposition is performed only by passing the substrate over the upper surfaces of the Cu target and Co target, and therefore the linetic energy created is small and the sputter molecules of a gradient component involving the gas are deposited at the same time, thereby impairing the smoothness of inter-layers of the artificial latticed multi-layer film and ending up with variations in the GMR characteristics and deterioration of the performance. In order to suppress the adverse effects caused by the oxygen content, which makes one of the factors causing the variations in the characteristics, an addition of hydrogen gas to the sputter gas such as argon and the like has been tried to solve this problem. However, a great difficulty involved with maintaining the amount of hydrogen gas to be added constant and also dangers of handling hydrogen gas have prohibited the use of this method together with the problem of depositing a metal on the surface of a glass substrate or a ceramic substrate containing a metal oxide due to the reaction of a very active reduction that takes place at the time of plasma discharge in an atmosphere added with hydrogen gas.
The present invention deals with the foregoing problems involved with the prior art film deposition apparatus and aims to provide an artificial latticed multi-layer film deposition apparatus that enables the film deposition of an artificial latticed multi-layer film realizing stable GMR characteristics readily.